Evaluating the overall population-level relevance of the current ecotoxicological tests using demographic model...

Ecotoxicological tests are usually designed to measure individual-level toxicity, such as impacts on survival rate and fecundity during specific life stages. To assess population-level chemical risk, ecotoxicological test results are often incorporated into theoretical population models. However, because test duration is generally shorter than the lifespan of the test species, not all survival and reproduction parameters required for constructing population models are measured. Current test protocols may therefore overlook individual-level chemical impacts crucial for population dynamics, potentially leading to inaccurate risk assessments. In this study, we evaluated the population-level relevance of the test protocols provided by the Organisation for Economic Co-operation and Development. We first compiled matrix population models that represented the full life cycles of the test species from published articles. We then aggregated the elasticities of the population growth rate to the parameters measured in the tests. The aggregated elasticity, ranging from 0 to 1, indicates how a slight change in vital rates measured in the test affects the population growth rate, representing the population-level relevance of the test protocols. The relevance score of each test was generally below 0.4 but varied depending on the endpoint type and the taxonomic group of the target species. Notably, tests designed for terrestrial invertebrates showed low relevance, indicating a substantial limitation in capturing individual-level defects that may lead to severe population decline in terrestrial invertebrates. Multiple tests targeting the same species covered the life history complementarily, and their combined use increased population-level relevance. This study provides the overall landscape of the relevance of current ecotoxicological tests to population-level risk assessment, highlighting key directions to better align with population conservation.